Abstract:At the beginning of 2020, the outbreak of the COVID19 pandemic has caused the suspension of various economic activities in China. As an important microeconomic entity, listed companies have inevitably been severely impacted. Taking the outbreak of COVID19 as the background of the event, this paper examines the relationship between the financing constraints of listed companies and the fluctuations of the company’s market value within a certain time window before and after the outbreak from the perspective of the cost of debt capital. The results show that the degree of financing constraints of listed companies is significantly negatively correlated with the cumulative excess return during the event window period, and the more severe the impact of COVID19, the stronger the degree of negative correlation between the degree of financing constraints and the company value. Further research shows that under the impact of COVID19, compared with the stateowned enterprises, the correlation between the corporate value of private enterprises and the degree of financing constraints is stronger, and the lower the degree of financial market development, the more significant the impact of financing constraints on corporate value.